Image: Baker; E.J. Keller/Smithsonian
There are plenty of reasons species go extinct. Perhaps they die en masse in a meteor event, or a new species comes along that outperforms or eats them. These days, humans can often play a role, like they did with the passenger pigeon — literally hunting it to extinction. But what happened to the thylacine, aka the Tasmanian tiger?
It's pretty obvious that humans dealt the final blow, hunting the animal to extinction in the early 20th century, only 150 years after the Europeans arrived in Australia. But the species was already in decline, having once roamed the Australian mainland. Through a genetic analysis, a team of Australian researchers thinks that a changing climate might have played an integral role in the species' decline.
Studying the thylacine's demise could be important for more reasons than historical, though. "Understanding the impact of past climate change on Australian native fauna and disentangling its effects from that of human pressure and invasive species is critical for understanding extinction risk and focusing conservation efforts in the future," the study authors write in the Journal of Biogeography.
Basically, it's important to figure out climate change's effects separately from other human-caused influences.
The study began with tissue samples from 81 thylacines (both from the Australian mainland and Tasmania) collected from museums. The researchers extracted, analysed and sequenced the tissue's DNA while avoiding contamination as best as they could, and built models to try and understand how the entire thylacine population changed over time.
Their data demonstrated that some time in the species' history, it split between an eastern and a western group — the western one on the Australian island was larger. The quick disappearance of that population without any loss in genetic diversity meant that these Australian thylacines must have gone extinct really quickly.
Many once thought the introduction of the dingo to Australia played a role in the thylacine's decline. But as Australian news outlets have reported in the past, that's unlikely. The lack of dingoes in Tasmania combined with the genetic data implied that the Tasmanian thylacines suffered from some other problem. The researchers therefore felt that an unstable climate pattern, particularly El Niño, was the main bad thing that could have happened to have produced their results in Tasmania, and would could have wiped out the Australian thylacine population.
At least one researcher not involved in the study, biologist Colin Groves, emeritus professor from Australia National University, wasn't ready to completely rule out the dingo as a cause of the thylacine's decline, according to Cosmos Magazine, though.
Obviously these are just models and the researchers felt that more research would be required to fully understand the thylacine's plight. And although the climate change presented here comes before widespread human drivers, it should still make you think. If we're changing the climate now, and prior climate change caused other species to go extinct, it's pretty clear we can expect our actions to send other species to the grave, too.